This application relates to optical polarization and use of optical polarization in optical communications.
Optical polarization is an important parameter of an optical signal can be used in various optical devices and systems. In some applications, optical polarization may cause technical difficulties. For example, in fiber optic communication systems, polarization-dependent effects in fibers and other devices, such as the polarization-dependent loss (PDL), polarization-mode dispersion (PMD) and differential group delay (DGD), can adversely affect the performance and proper operations of optical devices or systems.
Optical polarization may also be used to benefit various applications. For example, two orthogonal polarized beams can be easily separated as in optical disk drives and many other optical devices and systems. In optical communication systems, two optical beams with mutually perpendicular linear polarizations may be used to carry two different optical channels and hence can be used to double the capacity of the information carried at a particular optical wavelength. This mechanism is essentially a polarization multiplexing technique and can be used in combination with the wavelength-division multiplexing (WDM) to double the capacity of a given WDM system. Implementations of such polarization multiplexing can be used to improve the capacity of existing WDM systems at a low cost in comparison with building new WDM systems to meet the demand for increased communication capacity.